code: def test_empty_std_aggregation():
      aggr = StdAggregation()
  
      x = torch.empty(0, 6).reshape(0, 6)
      index = torch.empty(0, dtype=torch.long)
  
      out = aggr(x, index, dim_size=5)
      assert out.size() == (5, 6)
      assert float(out.abs().sum()) == 0.0
  
file_path: pytorch_geometric/test/nn/aggr/test_basic.py
imports: import pytest
  import torch
  import torch_geometric.typing
  from torch_geometric.nn import MaxAggregation, MeanAggregation, MinAggregation, MulAggregation, PowerMeanAggregation, SoftmaxAggregation, StdAggregation, SumAggregation, VarAggregation
label_desc: Use image node_id 4 for calling a global function with example usage: test_empty_std_aggregation() without return types